Process of making lithographic posters



G. N. PIFER. PROCESS OF MAKING LITHOGRAPHIC POSTERS.

APPLICATION FILED NOV-12, I917.

Patented Sept. 28, 1920.

'NITED srA'rEsY PATENT OFFICE.

GEORGE N. PIPER, OF OLE VELAN'D, OHIO, ASSIGNOR TO THE POSTERGBAPH COMPANY, OF CLEVELAND, OHIO, A. CORPORATION OF OHIO.

PROCESS OI MAKING LITHOGRAPHIC POSTERS.

Specification of Letters Patent.

Patented Sept. 28, 1920.

Application filed November 12, 1917. Serial No. 201,617.

To all whom it may concern:

Be it known that I, Gnonon N. PIFER, a

citizen of the United States, residing at Cleveland in the county of Cuyahoga and State of Ohio, have invented a certain new and useful Improvement in Processes of Making Lithographic Posters, of which the followlng is a full, clear, and exact description.

This invention relates to a process of making lithographic posters by photographic means, and has for its chief object to provide a method which will insure correct detail, likeness, reduced cost, and speed in roduction.

E till further the invention aims to provide a method which overcomes the disadvantages of the present method involving hand work on the part of the artist who is required to draw by hand the picture which is to be reproduced in poster form.

As is well known, in the usual method of producing a poster lithograph, the skilled artist draws the image or picture on a stone or metal plate, such as zinc, with a specially prepared greasy crayon. The plate whether of stone ork-metal, and with the picture drawn on it as above stated, is subsequently etched with acid solutions. This etching does not afieot the greasy ink drawing, but renders the remainder of the surface susceptible to holding moisture which will prevent it from taking ink while the surface on which the drawing is made by the greasy crayon will take ink during the subsequent printing, thus enabling the drawing to be reproduced in the press in poster form.

With this principle to start with, I dispense with the hand work'by producing the image on a suitable and practical support photographically, using for this purpose an enlarging camera by which the image can be photographed by projection on said prepared support, in the exact size or proportions desired, from a previously prepared small negative of the image or subject which is to be reproduced on the poster. This image is subsequently treated so as to make it susceptible to taking greasy ink with the image correctly interpreted in small closely spaced dots instead of a continuous tone, and after it has been inked it is transferred to the printing stone or plate which is then etched and handled in the same way as that following the hand work in the process ascarried on at the present time.

It should be understood that poster lithography means and involves the production of large effects. To obtain large pictorial results necessary for poster lithography, all known transfer methods are impractical and cannot be utilized.

For example, I might refer to a method which has been used to obtain small effects 1n which method there is utilized a bichromated gelatin surface, so insensitive to light action that it must be exposed in contact with a photographic negative under intense light. It is obvious that this process could not be used in poster lithography, for 1t would require negatives the size of a regulation poster sheet, 28x48 inches so that the expense would be absolutely prohibltive. Furthermore, on account of the nsensitiveness of the surface it would be impracticable to produce an image of the proper size by projection in an enlarging camera, which is one of the advantages of my process.

I might refer also to what is known as the collotype method which involves the making of a reticulated gelatin image on a hard level surface such as glass plate. This method has the same disadvantages, and the further disadvantage that in carrying out the method a paper transfer is pulled from the plate and transferred to the stone or zinc plate from which the printing is done. It has a further-"i disadvantage of stretching, rendering it "useless in a process which involves matching or registering different colors in the production of large effects such as posters.

All these disadvantages, as well as those enumerated in connection with the process involving the handwork by the artist are overcome by my invention which may be briefly summarized as consisting in certain novel steps of an improved method which will be hereinafter described in detail and set forth in the appended claims.

In the accompanyin sheet of drawings, Figures 1 and 2 show iagrammatically and in exaggerated manner my improved photographic paper at two different steps of the process.

In carrying out my process I start with a highly sensitized surface on an inexpensive paper base which is made waterproof is substantially non-stretchable, and is flexible, although the sensitized surface is level and rigid for all practical purposes. In producing this sensitized paper base a photographic paper stock 1 of suitable thickness is baryt-a coated as shown at 2, then smoothly calendered. Both sides are then preferably coated with a heavy solution of celluloid as shown at 3-3 which may contain about equal parts of celluloid and gum sandarac or copal. The latter prevents the coatmg of celluloid from becoming brittle, and makes the whole structure of the paper waterproof and pliable. I

Upon the baryta coated side is coated any suitable gelatin silver bromid emulsion 4, and when this is done the paper stock is ready for use, it being understood that the sheet is made in sufficient size for a regulation size poster, the dimensions of which were previously stated.

In the next step of the process the image or pictorial effect which is to be reproduced in poster form is photographed, that is to say, the image is exposed on the above described photographic base. In accomplishing this I use an enlarging camera, the image being enlarged from a suitable small negative. In thus making the enlarged image, the light rays are caused to pass through a finely grained screen which is only slightly separated from the sensitized sheet which must be held in flat condition very close and parallel to the screen. While I do not desire to be confined to any particular type or form of enlarging camera or photographic apparatus, I prefer to employ for this purpose the apparatus constituting the subject matter of my prior application, filed June 11, 1917, Serial N 0. 173,954, which shows one method by which a sheet of poster size may be held in absolutely flat condition very close to, but not touching the grained screen which can be supported any desired distance from the relatively small negative through which the rays pass from the source of light used in making the exposure. It will be understood that this will be done in a dark room, from which actinic rays are excluded.

Next, the exposed sheet is developed, rinsed, and fixed in the usual manner.

The developed image which is now what will exactly be transferred to the printing plate, and which is correctly interpreted in small dots due to the exposure through the grained screen, may by careful manipulation for the purpose of correcting color combinations, be locally reduced in some parts with any of the well known photographic reducing solutions.

Next the print is immersed in a suitable bleaching and tanning solution which may consist of cupric chlorid 4 grams, common salt 30 grams, water 240 c. c., to which is added 20 c. c. saturated solutlen of potassium bichromate. This treatment has a tanning action on that portion of the gelatin containing the reduced silver in the picture without affecting the other portions of the gelatin. In the drawings, 5 represents the dots of the image having been developed and tanned as decribed. It will be noted that the developed dot is shown clear through to the base 3 which is important.

After this tanning and bleaching of the image, the sheet is hung and dried and can be immediately etched with the regular etching or swelling solution which may consist of water three parts and glycerin 1 part, until the image just begins to show a relief upon the suface without any effect upon the under water-proof support or base. This swelling action is known in the trade by the term etching,hence the above statement, that the sheet is etched with the regular etching solution. All surplus moisture is then removed from the surface, and the sheet is then clamped down on a level plate. The image being as above stated bleached away, is at this stage scarcely visible.

Next the image is developed or rolled up in ink on the sheet by the application of a lithographic roller R and lithographic ink. In so doing, all that portion of the picture which had no development and tanning action, and which is permeated and moistened with etching or swelling solution refuses to take ink, while the tanned portions readily develop the image on the application of the ink by means of the lithographic roller as shown in Fig. 2. The necessity for photographing the image in the manner previously explained, through the screen, will now be apparent, for had the photographic image been produced in continuous tone, it could not now be reproduced or developed in the lithographic ink,-that is to say, it could not be developed in the satisfactory manner required commercially.

Next the image, which as before stated, is now developed in greasy ink with the lithographic roller, is transferred by a suitable press to the poster printing surface which may be stone or metal, and subsequently etched and treated in the usual lithographic manner. The poster printing can now be accomplished in the regular and well-known manner.

Thus it will be seen that the operator thus practically converts a photograph into greasy ink on a waterproof and level paper support in such a manner that the image or picture can readily be transferred to the machine printing surface. This support eliminates all danger of cockling in laying it down on the printing surface, and parts or sections not wanted for a certain color can be easily first cut away, or they can be eliminated by painting over such sections with water color pigment before the image is transferred or laid down on the printing surface.

In making multi-color posters it becomes necessary to make corrections, parts of the image, for instance, that are too strong can also be reduced by a splattering air brush. It is, of course, understood that whenever this water color paint is applied onto the sheet it prevents the ink from going onto the stone. None of these operations, however, affect the transfer sheet which is provided in the course of the process.

In making a multi-color poster, as many prints will be made with the photographing apparatus as there are colors to be printed, and as many images will be converted to greasy ink and transferred to the printing surfaces, that is to say, for a four color poster, four different enlargements or photographic images will be made and treated in the manner previously described. Their different depths can be determined and regulated by printing the photograph darker or lighter as the case may require. These separate prints which are subsequently converted or reproduced in ink represent the different color values to be printed in the usual manner in their successive order, when transferred in the manner above explained to the separate printing surfaces, thereby producing the multi-color printing effect.

Having described my invention, what I claim is:

1. The process of making a lithographic poster which comprises producing photographically upon a suitable base the subject of the poster correctly interpreted in dots or grain by projection from a small negative, and treating the base so as to cause the dots or grain to produce a relatively hard image for subsequent inking substantially as described.

2. The process of producing a lithographic poster which comprises producing a photographic enlargement from a small negative by projection with the photographic image correctly interpreted in dots or grain, and chemically hardening the dots or grain and treating the image so that the hardened portions will take reproducing ink.

3. The process of producing a lithographic poster which comprises producing a photographic enlargement from a small negative by projection with the photographic image correctly interpreted in hardened dots or grain, reproducing the hardened image in lithographic ink, and transferring the lithographic ink image to a printing surface.

4. The process of producing a lithographic poster which comprises making a photograph of the subject of the poster correctly interpreted in dots or grain by projection through a screen from a small negative, subj ecting the photograph to the action of tanning and etching solutions by which the portions represented by the dots or grain become relatively hard and the other portions become relatively moist.

5. Theprocess of making a lithographic poster which comprises producing on a waterproof flexible sheet a photographic enlargement from a relatively small photographic negative of the subject of the poster with the photographic image correctly interpreted in dots or grain, subjecting the surface of the sheet to the action of tanning and etching solutions, reproducing the image in lithographic ink with the image correctly interpreted in dots or grain, and transferring the same to a printing surface.

In testimony whereof, I hereunto aflix my signature.

GEORGE N. PIFER. 

